Animal Models for Limbal Stem Cell Deficiency: A Critical Narrative Literature Review

This literature review will provide a critical narrative overview of the highlights and potential pitfalls of the reported animal models for limbal stem cell deficiency (LSCD) and will identify the neglected aspects of this research area. There exists significant heterogeneity in the literature regarding the methodology used to create the model and the predefined duration after the insult when the model is supposedly fully fit for evaluations and/or for testing various therapeutic interventions. The literature is also replete with examples wherein the implementation of a specific model varies significantly across different studies. For example, the concentration of the chemical, as well as its duration and technique of exposure in a chemically induced LSCD model, has a great impact not only on the validity of the model but also on the severity of the complications. Furthermore, while some models induce a full-blown clinical picture of total LSCD, some are hindered by their ability to yield only partial LSCD. Another aspect to consider is the nature of the damage induced by a specific method. As thermal methods cause more stromal scarring, they may be better suited for assessing the anti-fibrotic properties of a particular treatment. On the other hand, since chemical burns cause more neovascularisation, they provide the opportunity to tap into the potential treatments for anti-neovascularisation. The animal species (i.e., rats, mice, rabbits, etc.) is also a crucial factor in the validity of the model and its potential for clinical translation, with each animal having its unique set of advantages and disadvantages. This review will also elaborate on other overlooked aspects, such as the anaesthetic(s) used during experiments, the gender of the animals, care after LSCD induction, and model validation. The review will conclude by providing future perspectives and suggestions for further developments in this rather important area of research.

Persistent loss of marginal corneal arcades after chemical injury

Changes in the limbal microvasculature following a chemical eye injury are essential for prognosis and management. At the slit lamp, it can be difficult to assess, here using fluorescein and indocyanine green angiography we show that anterior segment angiography may be informative to assess objectively the limbal microvascular changes over the follow-up period.

A systematic review of cellular therapies for the treatment of limbal stem cell deficiency affecting one or both eyes

PURPOSE

This systematic review (SR) assessed the efficacy, safety and cost-effectiveness of cell-based therapy to manage limbal stem cell deficiency (LSCD), a sight-threatening orphan condition most frequently associated with severe chemical or thermal burns. LSCD has historically been treated by transplanting limbal tissue. In 1997, a new treatment, cultured limbal epithelial autografts, was described for unilateral LSCD. In cases of bilateral disease cultured autologous oral mucosa stem cells have been used. The relative efficacy of different cultured tissue procedures is unknown.

METHODS

A protocol was registered with PROSPERO (CRD42017081117). Searches were conducted in 14 databases and 6 conference websites. Two reviewers independently selected studies, conducted data extraction and assessed risk of bias. One reviewer extracted individual patient data (IPD); a second checked extracted data. Data were assessed to determine the feasibility of statistical analysis, with Bayesian synthesis used to estimate improvement achieved by different treatments.

RESULTS

Fifty-two studies were eligible for inclusion (1113 eyes); 41 studies (716 eyes) reported IPD. No evidence was identified on cost-effectiveness. This SR was unable to confirm that any of the types of ex vivo cultured stem cell transplants identified for LSCD treatment were statistically superior when assessed against the outcomes of interest.

CONCLUSIONS

We believe this SR is the first to include IPD analysis of LSCD data. There is no evidence for the superiority of any method of limbal stem cell transplant. Confirmation of the safety and efficacy of this treatment modality is challenging due to heterogeneity within and between the studies identified. Therefore, recommendations for future research are proposed.

Technical Note: New similarity index for radiotherapy and medical imaging

PURPOSE

To describe a new similarity index and consider its biomedical applications.

METHODS

Similarity index for a pair of objects is defined by the number of shared features and total number of features in these objects. Similarity measure for more than two objects is commonly defined by using pairwise similarity indices. In the current study we suggest a novel similarity index which depends on the number of features shared between multiple objects and does not have the limitations of the recently described similarity measures. In order to introduce the new index, we consider a concept of "commonality." For a collection of sets A 1 , A 2 … , A N , commonality of a given element equals the number of sets this element belongs to. The similarity index for the compared sets is then defined by a weighted sum of normalized commonalities.

RESULTS

The considered biomedical applications of the proposed index include comparison of independent delineations of critical cranial structures in MR images and comparison of isodose distributions from different radiotherapy plans.

CONCLUSIONS

This study describes a novel similarity index which can be used to assess the similarity of multiple independent delineations of the anatomical structure or similarity of multiple dose distributions. Unlike the commonly used pairwise similarity indices, the new index is defined by the number of elements shared between multiple sets. Potential applications of the suggested similarity index for radiotherapy and medical imaging have been described.

CD200 Expression Marks a Population of Quiescent Limbal Epithelial Stem Cells with Holoclone Forming Ability

One of the main challenges in limbal stem cell (LSC) biology and transplantation is the lack of definitive cell surface markers which can be used to identify and enrich viable LSCs. In this study, expression of 361 cell surface proteins was assessed in ex vivo expanded limbal epithelial cells. One marker, CD200 was selected for further characterization based on expression in a small subset of limbal epithelial cells (2.25% ± 0.69%) and reduced expression through consecutive passaging and calcium induced differentiation. CD200 was localized to a small population of cells at the basal layer of the human and mouse limbal epithelium. CD200⁺ cells were slow cycling and contained the majority of side population (SP) and all the holoclone forming progenitors. CD200⁺ cells displayed higher expression of LSCs markers including PAX6, WNT7A, CDH3, CK14, CK15, and ABCB5 and lower expression of Ki67 when compared to CD200^- . Downregulation of CD200 abrogated the ability of limbal epithelial cells to form holoclones, suggesting an important function for CD200 in the maintenance and/or self-renewal of LSCs. A second marker, CD109, which was expressed in 56.29% ± 13.96% of limbal epithelial cells, was also found to co-localize with ΔNp63 in both human and mouse cornea, albeit more abundantly than CD200. CD109 expression decreased slowly through calcium induced cell differentiation and CD109⁺ cells were characterized by higher expression of Ki67, when compared to CD109^- subpopulation. Together our data suggest that CD200 expression marks a quiescent population of LSCs with holoclone forming potential, while CD109 expression is associated with a proliferative progenitor phenotype. Stem Cells 2018;36:1723-1735.

Portuguese recommendations for the prevention, diagnosis and management of primary osteoporosis - 2018 update

BACKGROUND

Advances in osteoporosis (OP)case definition, treatment options, optimal therapy duration and pharmacoeconomic evidence in the national context motivated the Portuguese Society of Rheumatology (SPR) to update the Portuguese recommendations for the diagnosis and management of osteoporosis published in 2007.

METHODS

SPR bone diseases' working group organized meetings involving 55 participants (rheumatologists, rheumatology fellows and one OP specialist nurse) to debate and develop the document. First, the working group selected 11 pertinent clinical questions for the diagnosis and management of osteoporosis in standard clinical practice. Then, each question was investigated through literature review and draft recommendations were built through consensus. When insufficient evidence was available, recommendations were based on experts' opinion and on good clinical practice. At two national meetings, the recommendations were discussed and updated. A draft of the recommendations full text was submitted to critical review among the working group and suggestions were incorporated. A final version was circulated among all Portuguese rheumatologists before publication and the level of agreement was anonymously assessed using an online survey.

RESULTS

The 2018 SPR recommendations provide comprehensive guidance on osteoporosis prevention, diagnosis, fracture risk assessment, pharmacological treatment initiation, therapy options and duration of treatment, based on the best available evidence. They attained desirable agreement among Portuguese rheumatologists. As more evidence becomes available, periodic revisions will be performed. Target audience and patient population: The target audience for these guidelines includes all clinicians. The target patient population includes adult Portuguese people. Intended use: These recommendations provide general guidance for typical cases. They may not be appropriate in all situations - clinicians are encouraged to consider this information together with updated evidence and their best clinical judgment in individual cases.

A percepção de secretários municipais de saúde sobre a gestão do trabalho e da educação na rede pública do Sistema Único de Saúde (SUS)

Resumo O artigo apresenta resultados de pesquisa empírica com secretários municipais de saúde de microrregião do Paraná, e tem por objetivo analisar os mecanismos da gestão do trabalho e da educação em saúde durante a implantação das redes de atenção básica na região. Utilizamos método integrado quali-quantitativo com questionário e entrevistas semiestruturadas realizadas com 24 gestores. O material foi transcrito, categorizado e analisado com o método de análise de conteúdo temático. Os resultados indicaram concepção reduzida quanto à gestão do trabalho e da educação, entendidos como processos autônomos entre si, limitada à oferta de cursos, sem uma compreensão das possibilidades de gestão integrada de educação e trabalho. Prevalece uma visão de gestão do setor público baseada no gerencialismo e na performatividade, consideradas tecnologias políticas neoliberais. Resultados apontam que, na percepção dos secretários municipais de saúde, as principais dificuldades para a implementação de ações educativas são: logística tempo/espaço para articular trabalho e formação, falta de interesse dos trabalhadores, determinantes externos de natureza política/jurídica. Entre os incentivos para a formação dos profissionais, surge majoritariamente a questão financeira, o que em momentos de crise econômica é preocupante, pois pode revelar paralisia nessas práticas de formação profissional. É preciso considerar, ainda, a existência de lacuna entre debate teórico no campo da educação em saúde e a discrepante realidade encontrada nesses municípios. Conclui-se indicando que, apesar de haver consenso da importância da educação em saúde para a qualidade da atenção e organização do processo de trabalho nos serviços de saúde, existe ainda longo caminho a percorrer para aprimorar a gestão pública dessas ações no Sistema Único de Saúde.

In vivo X-ray digital subtraction and CT angiography of the murine cerebrovasculature using an intra-arterial route of contrast injection

BACKGROUND AND PURPOSE

Investigation of the anatomy, patency, and blood flow of arterial and venous vessels in small animal models of cerebral ischemia, venous thrombosis, or vasospasm is of major interest. However, due to their small caliber, in vivo examination of these vessels is technically challenging. Using micro-CT, we compared the feasibility of in vivo DSA and CTA of the murine cerebrovasculature using an intra-arterial route of contrast administration.

MATERIALS AND METHODS

The ECA was catheterized in 5 C57BL/6J mice. During intra-arterial injection of an iodized contrast agent (30 μL/1 sec), DSA of the intra- and extracranial vessels was performed in mice breathing room air and repeated in hypoxic/hypercapnic mice. Micro-CTA was performed within 20 seconds of intra-arterial contrast injection (220 μL/20 sec). Image quality of both methods was compared. Radiation dose measurements were performed with thermoluminescence dosimeters.

RESULTS

Both methods provided high-resolution images of the murine cerebrovasculature, with the smallest identifiable vessel calibers of ≤ 50 μm. Due to its high temporal resolution of 30 fps, DSA allowed identification of anastomoses between the ICA and ECA by detection of retrograde flow within the superficial temporal artery. Micro-CTA during intra-arterial contrast injection resulted in a reduced injection volume and a higher contrast-to-noise ratio (19.0 ± 1.0) compared with DSA (10.0 ± 1.8) or micro-CTA when using an intravenous injection route (1.3 ± 0.4).

CONCLUSIONS

DSA of the murine cerebrovasculature is feasible using micro-CT and allows precise and repeated measurements of the vessel caliber, and changes of the vessel caliber, while providing relevant information on blood flow in vivo.

Maintained functionality of an implantable radiotelemetric blood pressure and heart rate sensor after magnetic resonance imaging in rats

Radiotelemetric sensors for in vivo assessment of blood pressure and heart rate are widely used in animal research. MRI with implanted sensors is regarded as contraindicated as transmitter malfunction and injury of the animal may be caused. Moreover, artefacts are expected to compromise image evaluation. In vitro, the function of a radiotelemetric sensor (TA11PA-C10, Data Sciences International) after exposure to MRI up to 9.4 T was assessed. The magnetic force of the electromagnetic field on the sensor as well as radiofrequency (RF)-induced sensor heating was analysed. Finally, MRI with an implanted sensor was performed in a rat. Imaging artefacts were analysed at 3.0 and 9.4 T ex vivo and in vivo. Transmitted 24 h blood pressure and heart rate were compared before and after MRI to verify the integrity of the telemetric sensor. The function of the sensor was not altered by MRI up to 9.4 T. The maximum force exerted on the sensor was 273 ± 50 mN. RF-induced heating was ruled out. Artefacts impeded the assessment of the abdomen and thorax in a dead rat, but not of the head and neck. MRI with implanted radiotelemetric sensors is feasible in principal. The tested sensor maintains functionality up to 9.4 T. Artefacts hampered abdominal and throacic imaging in rats, while assessment of the head and neck is possible.

Chemical detection of leukocytes in urine by means of a new multiple test strip

The performance of the leukocyte test area of the new multiple urine test strip, Multistix-10-SG, was evaluated in both field trials and model experiments. The detection limit was found to be adequate for routine purposes. Unspecific reactions are rare and generally indicated by the results of the other test areas.

Production and characterization of monoclonal antibodies specific to sweet clover necrotic mosaic virus

Monoclonal antibodies were produced in vitro by fusing mouse myeloma cells P3-X63-AgU1 with spleen cells derived from BALB/c mice immunized with purified sweet clover necrotic mosaic virus (SCNMV). Twenty-one out of 47 clones which secreted monoclonal antibodies of high titres against SCNMV were injected intraperitoneally into mice previously primed with Pristane. The ascites fluid harvested 10 to 14 days later showed a strong and specific anti-SCNMV activity in reverse passive haemagglutination inhibition, passive haemagglutination and indirect enzyme linked immunosorbent assay. The monoclonal antibodies of the 21 clones did not react with red clover necrotic mosaic virus (Swedish isolate). The class and subclass of immunoglobulins of the monoclonal antibodies secreted by established cultures were determined to be IgG2a for 15 clones and IgG3 for 6 clones.